RFR: JDK-8261510: Use RFC numbers and protocol titles in sun.security.ssl.SSLExtension comments [v3]

[John Jiang]

> This is a simple cleanup for sun.security.ssl.SSLExtension.
> The comments for the extension groups would use the RFC numbers and the protocol titles correspondingly.
> It also removes a trailing space in extension token_binding, and move signature_algorithms and signature_algorithms_cert to RFC 8446 extension group.

John Jiang has updated the pull request incrementally with one additional commit since the last revision:

  A extension group comment uses both of RFC number and protocol title

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2517/files
  - new: https://git.openjdk.java.net/jdk/pull/2517/files/84f131c0..f948498d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2517&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2517&range=01-02

  Stats: 63 lines in 1 file changed: 21 ins; 21 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2517.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2517/head:pull/2517

PR: https://git.openjdk.java.net/jdk/pull/2517